If I text or email a girl for info as to whether she's free at a certain time I don't expect an immediate answer, she might be with a booking, but arrive at the street and ring or text for the number at the arranged time and she had better be on the ball. I will wait maybe 5 minutes for a reply then I'm gone.
If I didn't get an answer for an info enquiry within an hour though I would move on, this particular sea is full of fish.